Interlocking control mechanism



June 2, 1959 G. R. TOWNSEND INTERLOCKING CONTROL MECHANISM 2 Sheets-Sheet 1 Filed 001;. 30, 1957 Inventor George R. Townsend,

b9 is Attorney.

June 2, 1959 G. R. TOWNSEND 2,889,421

INTERLOCKING CONTROL MECHANISM Filed Oct. 30, 1957' 2 Sheets-Sheet 2 6 or ge R. Townsend, bQLZVWMM s Attorney.

United States Patent INTERIJOCKING CONTROL MECHANISM George R. Townsend, Roanoke, Va., assignor to General Electric Company, a corporation of New York Application October 30, 1957, Serial No. 693,295

9 Claims. (Cl. 200-50) This invention relates to interlocking mechanism for circuit control equipment of the enclosed type having circuit control switches and separate access doors therefor, and it has for an object a provision of a simple, reliable and improved interlocking mechanism of this character. Such control equipment may include high voltage current limiting fuses, high voltage line isolating switches, and contactors of the electromagnetically operated type and their associated control devices mounted in suitable metal cabinets or compartments that may be assembled to meet widely varying circuit control requirements. Although not limited thereto, such variously assembled enclosed control equipment is particularly useful in high voltage heavy duty industrial motor control applications.

Frequently, in such control equipments one or more load circuits may be supplied through a switch which is not designed for circuit interruption, i.e. is not provided with are extinguishing means and in such cases a second switch designed for circuit interruption is provided between the load and the first switch. For example a relatively high voltage load may be supplied through a suitable switching device such as an electromagnetically operated contactor equipped with high voltage arc extinguishing means, and in order to make the equipment safe for repair and inspection an isolating switch is provided between the contactor and the high voltage supply terminals to disconnect the equipment from the line after the contactor has interrupted the circuit. Another load circuit comprising low voltage components such as contactor and relay operating coils or heating devices such as space heaters for motors may be supplied from the low voltage secondary winding of a stepdown transformer of which the high voltage primary is supplied through the contacts of the isolating switch. Since isolating switches are generally not equipped with are extinguishing means, a load interrupting switch is connected in the secondary circuit. Separation of the con- .tacts of the isolating switch prior to the extinction of the are at the contacts of either load-interrupting switch might result in a line-to-line short circuit at the high voltage -terminals of the equipment, and this in turn might cause an explosion with consequent serious injury to a personnel and equipment. Accordingly, a further object of the invention is the provision of interlocking means between a load-interrupting switch and a switch lacking adequate arc-extinguishing means which will prevent the separation of the contacts of the latter switch until sulficient time has elapsed for the arc at contacts of the loadinterrupting switch to be extinguished.

A more specific object of the invention is the provision of an interlocking mechanism which may be mounted in some location other than on the door of the cabinet in which the load interrupting switch is mounted.

In carrying the invention into effect in one form there of, a first switch which is of a type unsuited for circuit interruption, such as an isolating switch, is mounted in an enclosing casing. In a separate compartment provided with an access door is mounted a load-interrupting switch having an operating member which is accessible from outside the cabinet only through the open access door thus requiring the access door to be opened in order to open the switch. Between the two switches is an interlocking arrangement which enforces a time delay between the opening of the load interrupting switch and the opening of the first switch by requiring opening the load-interrupting switch and subsequent closing the access door to it in order to free the first switch for operation.

In illustrating the invention in one form thereof, it is shown as embodied in a motor control switching equipment enclosed within a metal enclosure having separate compartments and access doors for the isolating switch, electromagnetically operated contactor and low voltage equipment including a load-interrupting switch. The invention itself both as to the elements and their organization together with further objects and advantages will best be understood by referring to the following description taken in connection with the accompanying drawings of which Fig. 1 is a view in front elevation of a typical multiple tier cabinet assembly for enclosing high voltage three-phase motor control equipment to which the im-. proved interlocking mechanism of the invention may appropriately be applied shown with several of the compartment access doors open to reveal the motor circuit control switches therein; Fig. 2 is a view in perspective of a preferred form of the interlocking mechanism of the invention shown as applied to interlocking an isolating switch located in the top compartment and a load interruipting switch in the middle compartmentof the cabinet of Fig. 1; and Figs. 3, 4 and 5 are fragmentary views of the interlocking mechanism and the load interrupting switch which illustrate the positions occupied by the parts of the mechanism during successive stages of the operation and which therefore facilitate an understanding of the operation of the invention Referring now to the drawing and first to Fig. 1, in an upper compartment C1 of the enclosing cabinet 1 are mounted the current limiting short circuit protective fuses 2 and a three-phase gang disconnect switch 3 for isolating from the power lines 4, the fuses main starting contactor, and associated metering and control devices. The arrangement is such as to permit removal and replacement of a blown fuse only when the isolating switch 3 and theaccess door DC1 are open as shown. This switch is provided with an operating member which is illustrated as a shaft 5. As indicated in Fig. 2, this shaft 5 extends from the rear wall of the compartment C1 to the access door DC1 and is journalled for rotation in a bearing bracket 5a which is secured to the wall of cabinet 1 by any suitable means such for example as welding. In the end of the shaft 5 nearest the compartment access door DC1 is mounted a pin 6. The door-latching and unlatching handle 7 carries a yoke 8 which may be moved into engagement with the pin 6 for closing isolating switch 3 only when the access door is closed. Upon movement of the handle to its down position the latching dog 9 passes behind the lip 1a of the front cabinet wall and latches the door DC1 closed.

An interference member illustrated as a linkage rod 10 extends between the operating shaft 5 in the upper compartment C1 and the interference member of a motor starting switch in the lower compartment 02. This interference linkage rod 10 is mounted for vertical lengthwise sliding movement in guide brackets 10a and 10b secured to the side wall of the enclosing cabinet. Operation of the handle 7 to its isolating switch closing and latching position raises the interlocking linkage member 10 to move the latch 11 into latching relationship with the latching bracket 12. carried on the inside of the lower compartment access door D02. In this manner, access to the three-phase high voltage starting switch or contact 13, which is mounted in the lower compartment C2. and

connected in series with the isolating switch is prevented when the isolating switch is closed. Also, the possibility of closing the isolating switch and applying high voltage to the tips of the contactor while the access door DC2 is open is prevented by suitable means for blocking the upward movement of the linkage rod 10, until this door is closed. This means is illustrated as a spring biased interference bracket 11a mounted for lengthwise sliding reciprocating movement in a U-shaped bracket which is secured to the guide bracket b in a position such that the face of the upturned end of the interference bracket is engaged by the opposing face of the door latch when the door is closed. With the linkage rod 10 in its lower position, and the door open, the spring 1112 moves the bracket 11a over and past the upper edge of the bent end of latch member 11 to block the upward movement of the linkage rod. Consequently, the door DCZ must first be closed to free the rod 10 for upward movement in response to the closing movement of the isolating switch operating member.

The three-phase motor starting switch 13 is normally open and is electromagnetically operated to the closed position by means of a suitable electromagnet 14 which may be energized and deenergized by means of suitable manually operated switches, preferably of the pushbutton type, or by automatic control not shown.

For the purposes of preventing opening of the isolating switch when the motor-starting contactor 13 is closed and of preventing closing of the contactor unless the isolating switch is fully closed, the contactor is provided with interlocking means which coacts with the linkage rod 10. This interlocking means is shown as comprising an interference member which is illustrated as a bar 15 pivotally connected to the long arm of a motion-amplifying bell crank 16 of which the short arm is connected through a link 17 and other connecting means (not shown) to the movable contact-carrying member of the contactor. As shown in Fig. 2, the bell crank is pivotally mounted on a bracket 18 which may be secured to a suitable stationary member; for example it may be secured to the frame of the contactor. The interference member 15 is mounted in suitable mounting means e.g. guide blocks 19 and 20 to slide into and out of blocking relationship with the lower end of the interference link member 10. If the contactor is open the interference bar 15 is retracted to the left to unblock the rod 10 and free it for descent in response to opening of the isolating switch. When the isolating switch is open, rod 10 is in its lower position in which it blocks the interference bar 15 and thus prevents the contactors closing until the isolating switch is first fully closed to elevate the lower end of rod 10 out of blocking relationship. This permits the contactor to be closed and advance the interference bar 15 beneath the lower end of the rod 10 to block it in its elevated position and thereby prevent opening of the iso- I lating switch as long as the contactor remains closed. At the same time both access doors DC1 and DC2 are prevented from opening.

Between the operating shaft 5 and the driven member 10 is a yielding driving connection which provides for blocking the movement of the isolating switch operating shaft 5, if the interference member 10 does not move a predetermined distance from an initial position in response to a predetermined amount of movement of the operating shaft from a corresponding initial position. Illustrated as comprising the yielding driving connection are an arm 22 keyed to the shaft 5 and provided with pins 23 and 24, a bracket 25 secured to the interferencemember 10 and provided with a pin 26 together with a resilient member such as the coil spring 27 connected between pins 24 and '26 and stressed to bias the bracket 25 into engagement with pin .24. The free end of the bracket 25 is returned at right angles ;to act as the engagement surface of a driven member in thepath of pin 23. For actuating the isolating switch in response to Cir rotation of the operating shaft 5, a toggle mechanism comprising toggle arms 28 and 29 is connected between the shaft and the movable contact-carrying member of the isolating switch.

The driving connection between the operating shaft 5 and the interference member 10 is not my sole invention but is the joint invention of Richard E. Bonin and George R. Townsend, and is disclosed and claimed in an application S.N. 666,071, filed June 17, 1957, and assigned to the assignee of the present invention. The specific structure of this yielding driving connection is not essential to the present invention but is illustrated merely as an appropriate driving connection between the interference member 1% and the operating shaft 5. In its place could be used any other suitable driving connection such as that illustrated in application S.N. 638,618, Henry E. Trumpler, filed February 6, 1957, also assigned to the assignee of the present invention.

In the middle compartment C3 are usually located low voltage components such for example as meters, instruments, relays, a transformer for supplying power for space heaters and control power for contactor and relay operating coils, together with a secondary load switch 30 for interrupting the inductive secondary load circuit. The control supply transformer (not shown) is itself supplied through the isolating switch 3 in the top compartment C1. This control supply circuit is inductive owing to the number of operating coils and solenoids included. Since the isolating switch is an open blade knife switch without arc chutes or blowout, it must not be permitted to open the primary of the control circuit transformer and draw an arc because the are might reach over to the ground clips 30 and produce a line-to-ground short circuit. Under certain conditions of operation, even though the operating coil of the motor contactor 13 may be deenergized and the contactor tips physically open, the current across the tips may not have been ruptured. This is due primarily to the ionization phenomena present in the interruption of high voltage circuits. For example in the high voltage range, e.g. 2200-4490 volts the arc may hang on for fifteen or twenty cycles or even a full second or more.

For the purpose of preventing the isolating switch 3 from being open before the secondary load switch 30 is open or before current at the tips of the main motor contactor 13 has been ruptured, suitable interlocking means 31 are provided between the secondary load switch and the interference interlock rod member 10 which, as previously pointed out, has blocking and non-blocking positions with respect to the contact-opening movement of the isolating switch 3.

This interlocking means 31 is mounted together with the secondary load switch 30 on the inside wall of compartment C3 as best illustrated in Figs. 1 and 2. It comprises a bracket member 32 which is secured to the inside wall of the enclosing case 1 as shown in Figs. 1 and 2. This bracket serves as a mounting base for the secondary load switch 30 and the various parts of the interlocking mechanism. As shown, the switch 30 is mounted at the end of the bracket which is remote from the wall of the casing 1 to which the bracket is secured. The switch unit is provided with a push rod 33 which opens the switch contacts when it is depressed. For the purpose of actuating the push rod a lever 34 having an operating handle 35 is provided. The lever 34 is rigidly mounted on one end of a rotating shaft 36 on the other end of which is mounted a cam 37. A cam follower 38 which is pivotally mounted on a pivot 39 cooperates with the cam to depress the push rod 33 of the switch 30. In this connection the edge 38a of a notched portion of the cam follower bears against the surface 37a of the cam and, as viewed in Figs. 3, 4 and 5, clockwise rotation of switch-operating lever 34 produces clockwise rotation of the cam follower to depress the push rod and open the contacts of unloading switch 39.

answer Securely fastened on the vertical interference rod is a stop plate 40. A moving bolt 41 is slidably mounted in a U-shaped bracket 42 to move into the path of vertical movement of the stop plate. This U-shaped bracket is secured to a wall of the mounting bracket 32. Pivotally mounted on the hub which supports the shaft 36 is a freely rotating arm 43. On this arm at its lower end is mounted a pin 44 which engages the opposing surfaces in a slot 45 in bolt 41. The cam 37 is provided with a bifurcated portion which is best seen in Figs. 2 and 4. When shaft 36 is rotated the pin 44 bears against one or the other of the teeth 37b and 370 of the bifurcated portion.

Suitably secured to the inside wall surface of the door D03 of the middle compartment which houses the secondary load switch 30 and interlocking mechanism 31 is a bracket 46. With the various parts of the interlocking mechanism occupying the positions in which they are illustrated in Figs. 2 and 3, the bracket 46 can move in and out without engaging any element of the interlocking mechanism as the door is opened and closed. However, with the parts occupying the positions in which they are illustrated in Figs. 4 and 5, the bracket 46 will engage the arm 43 as the door is closed and rotated in a clockwise direction.

With the foregoing understanding of the elements and their organization, the operation of the interlocking system will readily be understood from the following detailed description.

As an initial operating condition it is assumed that doors DC1, DCZ and DC3 are all closed and that the isolating switch 3, secondary load switch 30 and main motor contactor 13 are also closed. As long as the contactor 13 is closed, the interference bar 18 maintains the vertical interference rod member 10 and its bracket 25 elevated in blocking relationship with respect to the opening movement of the isolating switch 3, and this prevents opening the door DC1 since rotation of shaft 5 and operating handle '7 which carries latch 9 is blocked. Likewise with rod 10, elevated door DCZ cannot be opened. Thus the isolating switch is locked closed and cabinet doors DC1 and DCZ are locked closed as long as contactor 13 is closed. Further, with the manual operating lever 34 rotated toward the door to close the secondary unloading switch 30, the tooth 370 of the bifurcated portion of the cam has advanced the bolt 41 beneath stop plate 40 and thus prevents descent of the rod 10.

Although it is not the recommended method of operation, it is possible for a careless operator to open the middle compartment door DC3 and deenergize the operating coil of the contactor 13 by actuating the lever 34 to open the secondary unloading switch 30. It is also possible for him with his other hand, substantially simultaneously to grasp the operating handle 7 and attempt to open the isolating switch 3. If the isolating switch could be opened before the current at the contactor tips is interrupted a damaging line-to-ground short circuit could result. However, this is prevented by interlocking mechanism which operates as follows. After the middle compartment door DCS is opened, the operating lever 34 of the secondary load interrupting switch is pushed toward the rear wall of the cabinet to rotate shaft 36 in a clockwise direction as viewed in Figs. 3, 4 and 5. This causes cam 37 to rotate the cam follower 38 in a clockwise direction to depress push rod 33 and thereby open the contacts of secondary load switch 30. The opening of these contacts removes all load from the secondary of the control power supply transformer which is located in the middle compartment but which is not illustrated in the drawing.

At the beginning of the initial part of the rotation of cam 37 the inner surface of tooth 37c is in engagement with the pin 44 and moves away from the pin as the clockwise rotation of the cam proceeds. Owing to the space separating the pin 44 from the inner surface of tooth 3712 no motion is imparted to the bolt 41 or to the arm 43 which carries the pin 44 during this initial stage of the cam rotation. However in the latter part of the rotation, the inner surface of tooth 37b engages the pin 44 and causes the arm 43 and pin 44 to rotate with cam 37. This causes the bolt 41 to move to the left as viewed in Fig. 4.

As the clockwise rotation of the switch-operating lever 34 proceeds, the arm 43 rotates in a clockwise direction from the horizontal position in which it is illustrated in Fig. 3. At the point in the rotation at which the lever 34 engages the stop pin 48, the arm reaches the elevated position in which it is shown in Fig. 4. In this position it is directly in the path of the bracket 46 on door DC3. At this point the bolt 41 reaches the position in which it is illustrated in Fig. 4 and thus has moved to approximately half the distance necessary to free the interference rod 10.

In order to free the rod, the door DC3 must next be closed to cause the door bracket 46 to engage the arm 43 and causes it to continue its clockwise rotation to its final position. This final movement moves the bolt 41 to its extreme left, completely unlatched position illustrated in Fig. 5. The time required to close the door DC3 to withdraw the bolt 41 and unlatch the vertical interference rod 10 is adequate for any are at the tips of the motor contactor 13 to become extinguished before the vertical rod 10 can be moved to unblocking position to free the contact-carrying member of the iso lating switch. The door handle 7 of the door DC1 may then be rotated in a clockwise direction to move the vertical interference member 10 and stop-plate 40 carried thereby downwardly and simultaneously to move the contact-carrying member of the isolating switch 3 to the contact-open position. The parts of the interlocking mechanism are now in the position in which they are illustrated in Fig. 5.

During the initial part of the withdrawal movement of bolt 41 the biasing spring 47 acts as a buffer to prevent the bolt from overshooting. As best seen in Figs. 2 and 4, arm 43 has a detent 43a which engages with the bentover portion 38b of cam follower 38 to hold the arm 43 in the ready position when the operator removes his hand from the manual switch-operating lever 34. It

will also be noted that the stop-plate 40 has a notched portion 40a at its upper end. In the fully open position of the isolating switch 3 the vertical interference rod 10 has descended to a position in which the notch 40a is directly opposite the right hand end of bolt 41. Should the door DC3 now be opened and the arm 43 consequently released, the spring 47 will cause the bolt 41 to move into notch 49a thereby to prevent any upward movement of the interference member 10. The result is that the isolating switch 3 can neither be opened or closed unless the door DC3 is closed.

To close the isolating switch 3 the operations are reversed. With the door DC3 closed the isolating switch is moved to the fully closed position. The door is then opened again and the switch-operating lever 34 is moved to the closed position to close the contacts of the secondary load switch 30. The motor contactor 13 may now be closed for resumption of operation.

Although in accordance with the provisions of the patent statutes, this invention is described as embodied in concrete form and the principle of the invention has been explained together with the best mode it is now contemplated applying that principle, it will be understood that the apparatus shown and described is merely illustrative and the invention is not limited thereto since alterations and modifications will readily suggest themselves to persons skilled in the art without departing from the true spirit of the invention or from the scope of the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a first switch, a casing, a second switch in said casing and having an operating member, a door in said casing providing access to said member from outside said casing and interlocking means between said switches preventing opening operation of said first switch until after opening operation of said second switch and responsive to opening of operation of said second switch and to a subsequent closing of said door to free said first switch for opening operation.

2. In combination, a first switch, a casing, a second switch mounted within said casing and having an operating member, a door in said casing providing access to said operating member, and means for imposing a time delay between the operation of said second switch and the operation of said first switch comprising interlocking means between said switches preventing opening operation of said first switch until after opening operation of said second switch and responsive to opening operation of said second switch and subsequent closing of said door to free said first switch for operation.

3. In combination, a first switch having a movable contact-carrying member, an interference member having blocking and non-blocking positions with respect to the contact-opening movement of said contact-carrying member, an enclosing casing having an access door, a second switch mounted within said casing and having an operating member inaccessible from outside said casing when said door is closed, and interlocking means responsive to operation of said second switch to the contactopen position and the subsequent closing of said access door to provide for movement of said interference member from said blocking position to said non-blocking position to free said first switch for operation to the contact-open position.

4. In combination, a first switch having a movable contact-carrying member, an interference member having blocking and non-blocking positions with respect to the contact-opening movement of said contact-carrying member, a casing, a second switch mounted within said casing and having an operating member, a door in said casing providing access to said operating member, and means for interposing a time delay between the opening of said second switch and the opening of said first switch comprising interlocking means responsive jointly to the operation of said second switch to the open position and the subsequent closing operation of said door to provide for operation of said interference member from said blocking position to said non-blocking position.

5. In combination, a first switch having a movable contact-carrying member, an interference member having blocking and non-blocking positions with resptct to the contact-opening movement of said contact-carrying member, a bolt for locking said interference member in said blocking position, an enclosing casing, a second switch mounted within said casing and having an operating member, a door in said casing providing access to said operating member from outside said casing, and means for inter-posing an interval of time between the opening of said second switch and the opening of said first switch. comprising bolt withdrawal means responsive to the switch-opening operation of said operating member and the subsequent closing of said door to free said interference member for movement to said non-blocking position to free said contact-carrying member for movement to the contactopen position.

6. In combination a first switch having a movable contact-carrying member, an interfering member having blocking and non-blocking positions with respect to the movement of said contact-carrying member, an enclosing casing having a door, a second switch mounted within said casing and having a switch-operating member accessible from outside said casing in the open position of said door, a bolt member having an advanced position Cir for locking said interfering member in said blocking position and a withdrawn position, and a bolt withdrawal member operable from an initial position to a preparatory position in response to operation of said switch-operating member and operable to a third position to withdraw said bolt in response to closing of said door.

7. In combination a first switch having a movable contact-carrying member, an interfering member having blocking and non blocking positions with respect to the movement of said contact-carrying member, an enclosing casing having a door, a second switch mounted within said casing and having a switch-operating member accessible from outside said casing in the open position of said door, a bolt member having an advanced position for locking said interfering member in said blocking position and a withdrawn position, a bolt withdrawal member having an initial position, a preparatory position and a final position in which said bolt is withdrawn, spring means biasing said bolt to said advanced position and said withdrawal member to said initial position, a mechanical connection between said switch operating member and said withdrawal member for operating said withdrawal member from said initial position to said preparatory position in response to operation of said switch operating member, and means moved by the closing of said door for operating said withdrawal member to said final position.

8. In combination a first switch having a movable contact-carrying member, an interfering member having blocking and non-blocking positions with respect to the movement of said contact-carrying member, an enclosing casing having a switch-operating member accessible from outside said casing in the open position of said door, means for interposing a time delay between the operation of said second switch and the operation of said first switch comprising a bolt member having an advanced position for locking said interfering member in said blocking position and a withdrawn position, and a bolt withdrawal member having an initial position, an intermediate preparatory position and a final position in which said bolt is withdrawn, a mechanical connection between said switch-operating member and said withdrawal member for operating said withdrawal member from said initial position to said intermediate position in response to operation of said switch-operating member, and means required to be actuated by the closing of said door for operating said withdrawal member to said final position thereby to provide for operation of said interfering member to said non-blocking position.

9. In combination, a first switch having a movable contact-carrying member, an interference member having blocking and non-blocking positions with respect to the contact-opening movement of said contact-carrying member, an enclosing casing having an access door, a second switch having an operating handle inaccessible from outside said casing when said door is closed, a bolt member, a bolt withdrawal member having a driven member, an actuating member on said door, spring means biasing said bolt member into position to lock said interference member in said blocking position and for biasing said driven member out of the path of said actuating member, and a driving connection between said operating handle and said withdrawal member for movingsaid driven member into the path of movement of said actuating member to provide for withdrawal of said bolt in response to subsequent closing said door to free said interference mcm her for movement to said non-blocking position.

References Cited in the file of this patent UNITED STATES PATENTS 1,741,227 Frank Dec. 31, 1929 2,604,796 Freese July 29, 1952 2,722,135 Taylor Nov. 1, 1955 2,780,685 Sprow Feb. 5, 1957 

